Power supply apparatus and power supply arrangement

1. A power supply apparatus, comprising: an interface to a load; at least one controllable solid-state switch for supplying power between the load and the power supply apparatus; and a controller that controls the at least one solid-state switch at a selected one of a plurality of permitted switching frequencies, the controller configured to limit the plurality of permitted switching frequencies on the basis of a determination of power loss of at least one solid-state switch, to compare noise levels of the load corresponding to the permitted switching frequencies, and to select, on the basis of the comparison, the switching frequency for which the noise level of the load corresponds to it is its smallest; wherein the noise levels of the load are determined at different switching frequencies such that local minimum points and maximum points of the noise level of the load are determined; and wherein the switching frequencies in the environs of which the noise level has local minimum points, and also the local minimums of the noise level corresponding to the switching frequencies, are determined.

2. Power supply apparatus according to claim 1 , further comprising: a network bridge and a load bridge connected to the load, the load bridge including a plurality of controllable solid-state switches, wherein the network bridge and load bridge are connected to each other with a direct-current intermediate circuit; and wherein the controller controls the solid-state switches of the load bridge at the selected frequency.

3. Power supply apparatus according to claim 1 , wherein the controller includes a memory, having stored therein a plurality of switching frequencies as well as the noise levels of the load that correspond to the plurality of switching frequencies.

4. Power supply apparatus according to claim 1 , wherein the switching frequency of at least one solid-state switch is selected by comparing the noise levels of the load that correspond to at least two switching frequencies, and wherein, on the basis of the comparison, the switching frequency for which the corresponding noise level of the load is smallest is selected.

5. Power supply apparatus according to claim 1 , wherein the switching frequency is selected repeatedly during the power supply.

6. A transport system, comprising: an electric motor for moving a transport appliance; a power supply apparatus connected to the electric motor, and including at least one controllable solid-state switch for supplying power between the electric motor and a power supply; and a controller that controls the at least one solid-state switch at a selected one of a plurality of permitted switching frequencies, the controller controlled to limit the plurality of permitted switching frequencies on the basis of a determination of power loss of at least one solid-state switch, to compare noise levels of the electric motor corresponding to the permitted switching frequencies, and to select, on the basis of the comparison, the switching frequency for which the noise level of the electric motor corresponding to it is its smallest; wherein the noise levels of the electric motor are determined at different switching frequencies such that local minimum points and maximum points of the noise levels of the electric motor are determined; and wherein the switching frequencies in the environs of which the noise level has local minimum points, and also the local minimums of the noise level corresponding to the switching frequencies, are determined.

7. A method for controlling at least one controllable solid-state switch a power supply apparatus, the method comprising: connecting a load to the power supply apparatus; determining noise levels of the load at different switching frequencies such that local minimum points and maximum points of the noise level of the load are identified; determining the switching frequencies in the environs of which the noise level has local minimum points, and also the local minimums of the noise level corresponding to the switching frequencies; limiting a plurality of permitted switching frequencies on the basis of a determination of power loss of at least one solid-state switch; comparing noise levels of the load corresponding to the permitted switching frequencies; and selecting, on the basis of the comparison, the switching frequency for which the noise level of the load corresponding to it is its smallest.